Sound propagation: Review nad tutorial

The reality of sound propagation in the atmosphere is more complicated than simple geometrical spreading above a flat hard ground. Most common grounds, such as grass covered ground and layers of snow, are acoustically soft. This implies a complex reflection coefficient leading to a measured spectrum that is strongly influenced by the type of ground surface between source and receiver. Grounds may not be flat, leading to shadow zones or alternatively multiple reflections at the ground. Gradients of wind and temperature refract sound either upwards (upwind or in a temperature lapse) or downwards (downwind or in a temperature inversion), also leading to shadow zones or multiple reflections, respectively. Atmospheric turbulence causes fluctuations and scatters sound into acoustical shadow zones. Many of these features mutually interact and accurate predictions of sound transmission from source to receiver must somehow account for all of these phenomena simultaneously.